One form of cooling system for nuclear reactors is a pressurized water system. The water is held under pressure by nitrogen gas to prevent boiling. Dissociated hydrogen and oxygen and radioactive contaminants are then withdrawn from the pressurized system in a nitrogen stream, and the hydrogen is recombined with oxygen into the safer and more easily handled water. In such recombiner systems, oxygen is added to the gas stream in an attempt to maintain a stoichiometric mix of hydrogen and oxygen in a nitrogen gas stream. The gases are then preheated and introduced into a catalytic reactor. The hydrogen and oxygen are there recombined in an exothermic reaction to form water vapor, which, after cooling, is separated from the nitrogen gas stream. The nitrogen is delivered to delay tanks where it is held for a length of time sufficient for decay of radioactive material. Some of the nitrogen gas from the delay tanks is returned to the recombiner system to maintain a large percentage of inert nitrogen gas in the recombiner gas stream.
To assure a stoichiometric mix of the hydrogen and oxygen in such systems, a sample of the nitrogen gas in the output stream is taken to determine the amount of oxygen and hydrogen gas remaining in that stream. An oxygen supply to the nitrogen stream at the recombiner input can then be controlled to hold the hydrogen and oxygen gases at the output to a minimum.
Prior recombiner systems have not responded well to transients in the inlet stream mixture. A five to ten second response time was required and in that time a dangerously high level of either hydrogen or oxygen could occur in the outlet stream.
An object of the present invention is to provide a recombiner system which maintains a stoichiometric mixture of component gases even with transient changes in hydrogen level in an inlet gas stream. A specific object of this invention is to provide a recombiner system which is able to respond to a change of hydrogen level of four percent within one-half second.